docs: def get_min_max_bounds(self):
          """
          Return a dict of min- and max-values for the given column.
          This is required to estimate the bounds of images.
          """
          bound = Bound(999999.0, 0.0)
          for bp in Breakpoint:
              bound.extend(self.get_bound(bp))
          return {'min': bound.min, 'max': bound.max}